Status of INSPIRE inspired OGC Web Services
F.J. Lopez-Pellicer, R. Béjar, W. Rentería-Aguaviva,
P.R. Muro-Medrano, F.J. Zarazaga-Soria
{fjlopez, rbejar, walterra, prmuro, javy}@unizar.es
Universidad de Zaragoza, Zaragoza, Spain
This work provides a quantitative and qualitative analysis of the evolution of the European OGC Web services landscape in the period 2010-2011 related with the European INSPIRE directive. The legislative transposition of the European INSPIRE Directive to national legislation across Europe is boosting the implementation of standard Geospatial Web services like OGC Web Map services (view services), OGC Web Feature services (download services), OGC Web Processing services (invoke spatial service services and transformation services), and OGC Catalogue services for the Web (discovery services). The maintenance of an updated list of Geospatial Web services, such as the lists related with the elaboration of the State of Play reports, has become a challenge.
OGC acknowledges that a registry of all OGC Web Services (OWSs) is needed for the community [1]. Construction of applications or portals depends on such registries. Several alternatives, such as UDDI Business Registries and CSW catalogues with specialized profiles, have been explored by OGC. The purpose of these registries is to answer the question what geospatial services exist globally based on the voluntary registry of service instances by service providers.
The use of service registries or catalogues for the discovering of Geospatial Web services in decision support and decision-making scenarios is the most popular assumption found in the literature [2,3]. However, the catalogue approach is based on the premise that all the Geospatial Web services are registered, and each service record contains an accurate description of the service. This is a quite strong assumption that frequently is not met in the geospatial domain [4]. In addition, the development of catalogue service standards by OGC is slow with few available implementations, especially if their numbers are compared with other specifications.
Search engines have revealed to be a surprising alternative for the discovery of geospatial Web services. For example, the investigation of Al-Masri et al. [5] found that all the web services that were discovered, 72% were found only in Web search engines, and detected a significant growth rate of services found in search engines. Basic heuristics derived from the signatures of OGC Web service methods have been exploited to discover references to the endpoints of Web Map Services (Refractions Research [6], Sample et al. [7]). Lopez-Pellicer et al. [8] reviewed these techniques and debunked some common assumptions on the discovery of geospatial Web services on search engines, such as that Google is the best search engine for finding OWSs or that the search of OWSs requires the use of complex search operators.
Nobody discuss today the role of search engines to locate information on the Web. Each day, users use the search engines for finding information (e.g. weather, news) and finding specific Web sites (e.g. a booking site, a personal page). At the same time, they use search engines for obtaining Web resources such as images and music files. First, search engines have indexed pages with information, sites, images and music files using Web crawlers. However, effective automated collection of OGC Web services goes beyond of standard crawling techniques. It requires the development of heuristics able to discover OGC Web services without explicit backlinks from geoportals. Web crawlers supply content to WMS directories, such as Skylab Mobilesystem [9] and Geopole [10]. Lopez-Pellicer et al. [11] generalized this approach for finding different kinds of OGC Web services in Europe and found 6,544 services.
This submission will analyse if the service registries have fulfilled their role as registries of all OGC Web services in Europe role and which are the alternatives. Then, it will present an analysis of the presence of OGC Web services in the European Web in January 2.011 and the evolution from January 2.010.
Acknowledgements
This work has been partially supported by Spanish Government (projects “España Virtual” ref. CENIT 2008-1030, TIN2009-10971) and GeoSpatiumLab S.L.
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